Sodium nuclear magnetic resonance imaging of myocardial tissue of dogs after coronary artery occlusion and reperfusion.

Nuclear magnetic resonance (NMR) imaging techniques have been applied to the observation of tissue sodium-23 in normal and ischemic canine myocardium. To produce a region of ischemia and infarction in the myocardium, in six dogs a coronary artery was subjected to 1 hour of surgical occlusion followed by 1 hour of reperfusion. The dogs were then killed and sodium-23 NMR images of the excised hearts were obtained using a high field NMR imaging system. These images were compared with tissue sodium contents measured by flame photometry. The regions of ischemic damage were clearly visible as areas of increased sodium NMR signal on the three-dimensional images. A good correspondence was found between the relative intensity of the sodium signals and the sodium contents of normal myocardium and myocardium subjected to coronary artery occlusion and reperfusion. The data suggest the feasibility of NMR sodium imaging to detect the location and extent of myocardial damage in patients with coronary artery disease.

Computed tomography of disseminated meningeal and ependymal malignant neoplasms.

We studied computed tomography (CT) scans of 50 patients with clinical signs and symptoms compatible with disseminated meningeal tumor, all documented by cerebrospinal fluid cytology, surgical biopsy or autopsy. Twenty-three patients also had nuclear scans, and 13 had cerebral angiograms. Represented in the series were patients with metastatic carcinoma, gliomas, and lymphomas. The characteristic CT findings included gyral enhancement without edema; sulcal and basilar cisternal obliteration and enhancement, and ependymal-subependymal enhancement. The correct diagnosis was made by CT in 28 of the 50 cases (56%).

Cerebrovasculopathy following irradiation in childhood.

Symptomatic intracranial vasculopathy developed in four patients following irradiation for central nervous system tumors. All the patients presented with a stroke-like picture from 2 to 22 years after the completion of radiotherapy. Two of the patients showed abnormalities on arteriography consisting of narrowing of the supraclinoid portion of the internal carotid artery and the adjacent proximal anterior and middle cerebral arteries. Although the risks of radiotherapy for central nervous system tumors of malignant potential are outweighed by potential benefit, the risks should be carefully considered in cases of tumors with little or no malignant potential.

Effects of radiographic contrast agents on spinal cord physiology.

Segmental reflexes in the spinal cords of cats anesthetized with chloralose were used to evaluate the neurophysiologic effects of radiographic contrast agents. The exposed lumbar spinal cord was bathed with concentrations of ionic and nonionic agents including saline, sodium meglumine diatrizoate, meglumine iothalamate, meglumine iocarmate, and metrizamide. The following responses were evaluated: flexor and extensor monosynaptic reflex; polysynaptic flexion reflexes; spontaneous ventral root activity. Hypertonic solutions generally produced a transient decrease in all reflex activity for up to 1 hour. Isotonic solutions produced no significant changes in the monosynaptic responses, but an increase in amplitude of polysynaptic responses, and increased spontaneous activity. The usual facilitory effects of flexion reflex on the flexor monosynaptic reflex were unchanged, but the expected inhibitory effect of flexion reflex on the extensor monosynaptic reflex was changed to excitatory. The relative ability to produced these effects was sodium meglumine diatrizoate greater than meglumine iothalamate greater than meglumine iocarmate greater than metrizamide.

Safety and efficacy of iopromide in cerebral arteriography.

RATIONALE AND OBJECTIVES: Iopromide is a new nonionic monomeric contrast medium for cerebral arteriography. This agent has been approved for sale in over 45 countries; however, it is still undergoing clinical review in the United States. This study evaluated the safety and efficacy of iopromide in comparison with two other nonionic contrast media. METHODS: A total of 173 patients participated in the study, which was prospective, double-blind, and randomized. In two centers, patients received iopromide or iohexol; in the other three centers, patients received iopromide or iopamidol. Adverse events were monitored by investigators, and efficacy was evaluated by grading the radiographic images. RESULTS: Most adverse events were mild or moderate in severity; all resolved completely. Twenty-one percent of patients given iopromide were reported to have a drug-related adverse event, versus 44% of patients given a comparator. No statistically significant difference emerged between iopromide and the comparators with regard to efficacy. CONCLUSIONS: These study results indicate that iopromide is a safe and effective contrast medium for cerebral angiography.

Recognition and differential diagnosis of enlarged extraocular muscles in computed tomography.

We found enlargement of the extraocular muscles in 70 patients out of 603 orbit studies, of whom 310 had exophthalmos. The majority (46 of 70) had the eye signs of Graves' disease. Arteriovenous malformations and carotid cavernous fistulas can cause enlargement of the extraocular muscles by a diffuse increase in orbital venous pressure, Acute orbital myositis can be distinguished from other forms of pseudotumor by the presence of a single enlarge extraocular muscle with associated inflammatory findings which responds to corticosteroid therapy. Neoplasms may invade extraocular muscles or compress their venous drainage causing secondary muscle enlargement. In all these patients the presence of a mass was correctly identified. The ability of the computed tomography scanner to recognize abnormalities of the extraocular muscles represents a significant advance in classification and diagnosis of the causes of exophthalmos.

MR findings in patients with subacute necrotizing encephalomyelopathy (Leigh syndrome): correlation with biochemical defect.

MR studies were correlated with biochemical results in nine children who presented with lactic acidosis and/or abnormal MR findings in the basal ganglia. Neurologic development was delayed in all nine children. Seven of these patients were diagnosed as having subacute necrotizing encephalomyelopathy (SNE, or Leigh syndrome) on the basis of history, clinical findings, and biochemical studies; of the remaining two, one had congenital lactic acidosis and the other had familial bilateral striatal necrosis with no known biochemical correlate. Although the clinical presentation of these patients was similar, we found distinctive MR abnormalities in characteristic locations in the seven patients with SNE, with or without detectable specific mitochondrial enzyme deficiency in cultured skin fibroblast assays. In our case studies of SNE patients with detectable enzyme deficiency states, defects in pyruvate dehydrogenase complex and cytochrome c oxidase have been found. The MR finding of note in SNE is the remarkably symmetrical involvement, most frequently of the putamen. In our study, lesions were also commonly found in the globus pallidus and the caudate nucleus, but never in the absence of putaminal abnormalities. Other areas of involvement included the paraventricular white matter, corpus callosum, substantia nigra, decussation of superior cerebellar peduncles, periaqueductal region, and brainstem. In patients who present with lactic acidosis and whose MR findings show symmetrical abnormalities in the brain, but with sparing of the putamen, the diagnosis of SNE is in doubt.

Multifocal hypointense cerebral lesions on gradient-echo MR are associated with chronic hypertension.

PURPOSE: To investigate the basis for multifocal hypointense lesions within the brain as identified on T2*-weighted gradient-echo MR imaging in patients with no known or presumed cause of these lesions. METHODS: In the first of a two-part study design, we retrospectively reviewed a case series of 38 patients whose gradient-echo MR images showed multiple hypointense lesions within the brain parenchyma. Thirty-one cases in which the cause was known or presumed (eg, head trauma or cavernous angioma) were excluded from further review. The MR studies and clinical findings of the remaining seven cases were reexamined. In the second part, using a cohort study design with respect to hypertension, we prospectively reviewed the gradient-echo images from MR studies of 65 patients and control subjects enrolled in two ongoing clinical studies, one on "possible vascular dementia" (n = 33) and the other on "possible motor neuron disorder" (n = 32). RESULTS: In the first part of the study, we found seven cases with a pattern of multiple hypointense lesions involving the deep gray matter nuclei, especially the basal ganglia (n = 6) and thalamus (n = 5). In addition, involvement of the corona radiata (n = 5), brain stem (n = 4), and cerebellum (n = 3) was seen. Clinical review revealed a history of chronic hypertension in all seven patients. In the cohort study, we found three of 65 persons who had two or more focal hypointense lesions that involved the basal ganglia or thalami. Review of the clinical data showed that all three patients were being treated for hypertension; also, all three were patients from the "possible vascular dementia" group. CONCLUSIONS: The MR imaging pattern of multifocal hypointense lesions within the basal ganglia, thalamus, and other deep cerebral structures is more commonly found among patients with a history of chronic hypertension than in patients without chronic hypertension.

Computed tomography of primitive neuroectodermal tumors.

The primitive neuroectodermal tumor is a neoplasm of young individuals that occurs predominantly in the supratentorial compartment. It appears on computed tomography as a bulky mass, often with calcification with predominantly homogeneous enhancement but on occasion with cystic or necrotic areas. Cerebrospinal fluid seeding was observed in more than half the cases in our series. The patients had a short survival period (7-24 months). Despite surgery, radiation, and chemotherapy, further growth of this tumor has not been prevented.

CT of subarachnoid hemorrhage due to ruptured aneurysm.

Computed tomographic scans in 81 consecutive patients wih subarachnoid hemorrhage due to ruptured aneurysm were analyzed for patterns of hemorrhage and lucency and correlated with the development of spasm and hydrocephalus. The circulation time was measured angiographically in representative cases of spasm. Hemorrhage corresponded in a general way to the fossa of aneurysm origin and, when there was parenchymal or ventricular hemorrhage, in more specific ways to anterior communicating, middle cerebral, and posterior inferior cerebellar artery aneurysms. Basal ganglionic hemorrhages due to aneurysm ruptures occurred in two cases and could not be distinguished by appearance from hypertensive hemorrhage. Regions of low attenuation (lucencies) were often persistent and had lateralizing value; they showed a high correlation with arterial spasm. Conversely, spasm, particularly of a distal type, showed a significant correlation with increased circulation time and the occurrence of brain lucency. In cases of multiple aneurysms arising from different vessels in which there was hemorrhage or lucency, CT scans correctly predicted the site of aneurysm in 77% of cases. Periventricular lucency was a weak predictor of progressive hydrocephalus, while an intraventricular hemorrhage was a strong predictor of moderate to severe hydrocephalus.

Reversible signal abnormalities in the hippocampus and neocortex after prolonged seizures.

PURPOSE: To investigate the phenomenon of reversible increased signal intensity of medial temporal lobe structures and cerebral neocortex seen on MR images of six patients with recent prolonged seizure activity. METHODS: After excluding patients with known causes of reversible signal abnormalities (such as hypertensive encephalopathy), we retrospectively reviewed the clinical findings and MR studies of six patients whose MR studies showed reversible signal abnormalities. MR pulse sequences included T2-weighted spin-echo coronal views or conventional short-tau inversion-recovery coronal images of the temporal lobes. RESULTS: All six MR studies showed increased signal intensity within the medial temporal lobe, including the hippocampus in five studies. All follow-up MR examinations showed partial or complete resolution of the hyperintensity within the medial temporal lobe and the neocortex. In one patient, results of a brain biopsy revealed severe cerebral cortical gliosis. Temporal lobectomy performed 4 years later showed moderate cortical gliosis and nonspecific hippocampal cell loss and gliosis. CONCLUSION: Significant hyperintensity within the temporal lobe is demonstrable on MR images after prolonged seizure activity, suggestive of seizure-induced edema or gliosis. Damage to medial temporal lobe structures by prolonged seizure activity indicates a possible mechanism of epileptogenic disorders.

Computed tomography of the anteverted internal auditory canal.

A symmetric variation in the course of the internal auditory canals, visualized best on axial computed tomographic views with thin sections, was observed in three of 75 patients examined mainly for hearing, vestibular, and facial nerve dysfunction. The incidence may be lower in an unselected population. In coronal section, with either pluridirectional or computed tomography, an anteverted internal auditory canal may mimic the normal configuration of "medial narrowing" because of the effect of partial sectioning of an angled cylinder with a thin beam. The pathologic significance of this finding is uncertain. In the three cases reported, it was associated with adult-onset uni- or bilateral hearing loss. Vestibular function may be compromised but may not be symptomatic. Facial nerve function was not impaired.

Patterns of spinal cord atrophy by metrizamide CT.

Forty patients with cervical myelopathy underwent high-resolution computed tomography (CT) with intrathecal administration of metrizamide for evaluation of cervical spinal cord atrophy. Thirty of them showed evidence of either focal atrophic distortion or generalized accentuation of the anatomic surface features of the spinal cord. Patients with a Chiari malformation or syringomyelia were excluded. The characteristic features in cervical spondylosis and canal deformity include flattening of the ventral surface of the cord, central infolding, beaking of the lateral funiculi, and wasting of the dorsal surface of the cord. Patients with motor neuron disease showed a combination of anterolateral and posterolateral atrophy reflecting underlying degeneration of the anterior horn cells and/or corticospinal tracts, respectively. Those with monomelic motor neuron disease had a striking ipsilateral hemiatrophy of the spinal cord. Among those presenting with spastic paraparesis, seven with clinically definite multiple sclerosis showed diffuse atrophy or focal degeneration due to a localized plaque of demyelination. Two cases of cord neoplasm showed atrophy secondary to ascending or descending degeneration of the long tracts.

Computed tomography of the cervical lymph nodes: use of intravenous contrast enhancement.

Intravenous contrast administration increases the sensitivity of computed tomographic scanning for enlarged cervical lymph nodes but requires a detailed knowledge of neck anatomy, especially in order to distinguish certain normal vessels from involved nodal groups. Along the collar chain, relations between the parotid and submandibular salivary glands and the posterior and anterior facial veins and facial artery are analyzed. The digastric muscle is defined as a transitional landmark between collar and deep cervical nodes. Along the deep cervical chain, emphasis is on the internal jugular vein, its variability in size, and its relations to the anterior scalene and omohyoid muscles.

In vivo NMR imaging of tissue sodium in the intact cat before and after acute cerebral stroke.

The first in vivo nuclear magnetic resonance (NMR) images of tissue sodium in the intact animal are presented. The distribution of sodium in the normal cat's head is described. An experimental stroke was surgically induced. Sodium NMR imaging showed a pronounced focal increase in cerebral sodium concentration 9 hr after ligation of the middle cerebral artery. The method appears to be very sensitive for early detection of infarction. The measured increase in the regional sodium NMR signal probably reflects both a true increase in concentration of brain sodium and an increased NMR visibility of the sodium nucleus in the region of the infarction.

Noise considerations in dual energy CT scanning.

Dual energy CT scanning (tomochemistry) has been proposed as a method for determining various parameters relating to the elemental composition of the tissues. In this paper, our aim is to study the relative noise inherent in two proposed techniques for dual energy scanning; a "two crystal" technique and a "two kV" technique. In the two crystal technique, a split crystal detector is used to simultaneously obtain the high and low energy data during one scan at high kV. The two kV technique requires two scans taken with widely different kV settings. We first review three commonly used approaches for utilizing the scan data to compute the relevant parameters. A theoretical formalism is constructed which aids in understanding these methods. Then this formalism is used to study the influence of CT image noise on measurement precision in the case where the unknown parameters are densities. It is shown that, (1) the unavoidable overlap in the spectral data obtained by the two crystal technique results in a much lower signal-to-noise ratio than can be obtained by using the two kV technique, (2) the necessity for hard filtration of the high energy beam in the two kV technique has not heretofore been appreciated, and (3) the dose for a given x-ray tube heat load is also lower with the two kV technique.

CT of the nasopharyngeal region. Normal and pathologic anatomy.

The soft tissue anatomy of the nasopharynx is presented in terms of deglutitional and masticatory muscle layers. Within this framework of analysis, computed tomography can detect relatively early soft tissue changes of nasopharyngeal carcinoma.

The carotid region: normal and pathologic anatomy on CT.

The carotid region of the neck is defined in terms of three longitudinally oriented spaces: parapharyngeal, carotid, and paraspinal. Displacements of these spaces by neurogenic tumors of the neck are analyzed. The CT appearance and histology of these tumors are correlated.

Computed tomographic demonstration of giant aneurysms of the vertebrobasilar system: report of eight cases.

Giant aneurysms of the vertebrobasilar system can easily mimic other mass lesions in the posterior fossa and 3rd ventricle. Recently, we treated eight cases of giant aneurysm in the vertebrobasilar circulation that were demonstrated by computed tomography with angiographic correlation. We describe the salient radiological features that help to distinguish giant aneurysms from neoplasms and discuss their clinical manifestations and surgical management.

Hemangiopericytomas of the spine.

Four cases of hemangiopericytoma of the spine are reported. These are rare tumors that arise from the pericytes. Due to their invasive nature and marked vascularity, and detailed radiological work-up including computed tomography and spinal angiography should be obtained before a direct surgical attack is performed. Embolization of the tumor may also be quite helpful before surgical excision and has allowed a gross total removal of the tumor in two of the cases.